The study looked at the risk of mania and bipolar disorder in people who were hospitalized or visited the emergency room due to the use of hallucinogens. It included 9.3 million people aged 14–65 years, of whom 7,285 had hallucinogen-related acute care. Over three years, 1.43% of these people had an episode of mania, which is 25 times higher than in the general population (0.06%). After adjusting for age, sex, and other factors, the risk of mania in these people was 6 times higher (HR 5.97). The risk of a new diagnosis of bipolar disorder was 3.75 times higher (HR 3.75), the absolute proportion was 2.5% versus 0.11% in the general population. The study only involved people who needed acute care, and the results may not apply to all hallucinogen users. The findings point to the need for caution when using hallucinogens, especially in people at risk of bipolar disorder.